I got DSI Tetra new many years ago. It has been discontinued for some time. Some say it is four voice module of Prophet 08. Actually it is four voice version of DSI Mopho. Mopho took Prophet 08’s voice and added some features. Same features are are in Tetra. Programming Tetra requires lot of menu diving or software controller. I haven’t used it that much because of menu diving and because software controllers haven’t been that good. I made Device Panel for it in Cubase. Now it is more usable and it became one of my favorite synths. Before it was just good sounding synth. Editor’s note: This was written before I learned how useless device panels are. Got new vst editor witch works better than old one. Now I am using that.
If you are planning to do your own controller you should know midi implementation chart has one error. Unison Mode has NRPN number 95 and Key Mode NRPN number 96. In midi implementation chart they are other way around. Took some time and testing to figure that out. Otherwise midi implementation and chart are among best ones I have worked with. In fact it is so good I start to regret not getting Prophet 12 module when they still made it. It was almost as small. I am running out of room. So small but powerful is really good.
I didn’t know how much modulation options Tetra has. VST controller I had didn’t have best possible layout. Which is weird. I added controllers in order they are in midi implementation chart and got pretty usable interface. There was about eight controller I put in different place in about 90 controllers. Don’t understand how maker of VST controller messed it up so badly. Editor’s note: Actually vst controller had problem with drop downs which made modulation matrix hard to use. You can’t buy that version anywhere. In new one those work.
To modulation options. You have four LFOs and three envelopes and mod wheel, pressure and other control sources. Each have dedicated modulation destination selection except amp and filter envelopes. Addition to that you get four slot modulation matrix with 20 sources and 47 destinations. All this is behind menu diving unless you have some kind of controller on computer. This is lot and I still haven’t touched step sequencer.
Sound wise Tetra can do everything Prophet 08 can do except more than four voice polyphony. Addition to Prophet 08 Tetra has feedback which gives sound nice dirt and character. Don’t remember was there something else what Prophet 08 doesn’t have. Feedback makes Tetra sound quite different. It was designed for monophonic use but it works on polyphonic sounds too. Dirt works on polyphonic sound even when that seem to be mostly reserved for monophonic synth and sounds. Tetra shows polyphonic synth can be based on monophonic designs. Analog Four does that too. I wish Waldorf would make six or eight voice version of Pulse 2. I don’t mean paraphony which it already has but four or eight voices of its monophonic sound. You could make really nice pads with it.
Tetra has one missed opportunity and one weird design choice. You can’t turn Tetra off. You have to unplug it to turn it off. Don’t know if there absolutely was not room for power switch. It is bit annoying. Tetra has polychain where you can connect other Tetras to get more polyphony. Problem is all Tetras need own channels in mixer or DAW. Tetra has four audio outs but no audio in. I would have preferred to have audio in where you can direct output of slave Tetra. Then master Tetra could have mixed slave’s audio to correct level if there is any need for that. That way polychain could have been useful. Someone probably had 16 voice Tetra to show it works but it isn’t too useful.
I wish four voice polyphony wasn’t some sort of standard for smaller and cheaper analog synths. You can play chords and melody with four voices if you are careful. Fifth and sixth voice would help. I know there is Prophet Rev 2 which is upgrade to Prophet 08 but that doesn’t have feedback which I like so much. If this had six voices I wouldn’t be looking for more than four voice polyphonic analog synth.